Method for creating a film cooled article for a gas turbine engine

ABSTRACT

A method for finishing a film cooled article includes providing a film cooled article including at least one inner cooling plenum and at least one opening connecting the inner cooling plenum to an exterior surface of the film cooled article, positioning a machining element in contact with the exterior surface of the film cooled article, automatically moving the machining element along the exterior surface while maintaining contact between the machining tool and the surface, identifying an actual position of at least one film opening based on sensory feedback from the machining element using a controller, removing material from the exterior surface at the at least one film opening using the machining element, thereby creating a depression at the at least one film opening.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to United States ProvisionalApplication No. 62/012594 filed Jun. 16, 2014.

TECHNICAL FIELD

The present disclosure relates generally to film cooled articles for gasturbine engines, and more particularly to a method for creating a filmcooled article.

BACKGROUND

Gas turbines include a compressor section that compresses air and feedsthe compressed air to a combustor through a primary flowpath. Compressedair is mixed with fuel in the combustor and ignited, creating combustiongasses. The combustion gasses are expelled from the combustor through aturbine section, along the primary flowpath. As the combustion gassespass through the turbine section, each stage of the turbine section isdriven to rotate by the combustion gasses. Each stage is connected to acentral shaft, and the rotation of the turbine stage is transferred tothe shaft, thereby driving the shaft to rotate. In some implementations,such as a geared turbofan (GTF) engine, the rotation of the shaft drivesa fan. In other gas turbine implementations, such as a land basedturbine, the rotation of the shaft is output to an electrical generator,or another system requiring a rotational input.

To facilitate turbine operation, gas turbines include one or moreturbine stages, with each stage having multiple blades arrangedcircumferentially in the flowpath at a single axial position. Each bladeis paired with a corresponding vane. Due to the extreme temperatures ofthe combustion gasses, it is common practice to cool the blades andvanes to improve their ability to endure extended exposure to the hotcombustion gasses. In some examples, relatively cool pressurized air isprovided from elsewhere in the engine to the blades and vanes andoperates as a coolant. In such an example, the blades are referred to asfilm cooled articles.

SUMMARY OF THE INVENTION

A method for finishing a film cooled article according to an example ofthe present disclosure includes providing a film cooled articleincluding at least one inner cooling plenum and at least one openingconnecting the inner cooling plenum to an exterior surface of the filmcooled article, positioning a machining element in contact with theexterior surface of the film cooled article, automatically moving themachining element along the exterior surface while maintaining contactbetween the machining tool and the surface, identifying an actualposition of at least one film opening based on sensory feedback from themachining element using a controller, removing material from theexterior surface at the at least one film opening using the machiningelement, thereby creating a depression at the at least one film opening.

In a further embodiment of any of the foregoing embodiments, the filmcooled article is a cast film cooled article.

In a further embodiment of any of the foregoing embodiments, identifyingthe actual position of the at least one film opening based on sensoryfeedback from the machining element comprises interpreting sensorreadings from at least one of a touch sensor apparatus and a visualsensor apparatus using the controller.

In a further embodiment of any of the foregoing embodiments, identifyingthe actual position of the at least one film opening based on sensoryfeedback from the machining element comprises the controllerinterpreting sensor readings from a combination of a touch sensorapparatus and a visual sensor apparatus.

In a further embodiment of any of the foregoing embodiments, identifyingthe actual position of the at least one film opening based on sensoryfeedback from the machining element, and removing material from theexterior surface at the film opening using the machining element,thereby creating a depression at the film opening is repeated for eachfilm opening of the film cooled article.

In a further embodiment of any of the foregoing embodiments, identifyingthe actual position of the at least one film opening based on sensoryfeedback from the machining element, and removing material from theexterior surface at the film opening using the machining element,thereby creating a depression at the film opening is repeated for asubset of a plurality film openings of the film cooled article.

In a further embodiment of any of the foregoing embodiments, removingmaterial from the exterior surface at the film opening using themachining element, thereby creating a depression at the film openingcomprises removing material only at the film openings.

In a further embodiment of any of the foregoing embodiments, identifyingan actual position of at least one film opening based on sensoryfeedback from the machining element is performed by the controller inreal time as the machining element is moved along the exterior surface.

A further embodiment of any of the foregoing embodiments includesautomatically moving the machining element along the exterior surfacewhile maintaining contact between the machining tool and the surfacecomprises moving the machining element to an expected position of atleast one film opening.

In a further embodiment of any of the foregoing embodiments, identifyingan actual position of at least one film opening based on sensoryfeedback from the machining element using a controller comprisesidentifying the expected position and identifying the actual positionrelative to the expected position.

In a further embodiment of any of the foregoing embodiments, removingmaterial from the exterior surface at the film opening using themachining element, thereby creating a depression at the film openingcomprises creating a depression only at the film opening.

A finishing apparatus for a film cooled article according to an exampleof the present disclosure includes a central control machine including acomputerized controller, at least one articulating device controlled bythe central control machine, a machining tool mounted to thearticulating device, such that the articulating device is operable tomove the machining tool, at least one of a touch sensor apparatus and avisual sensor apparatus mounted to the machining tool andcommunicatively coupled to the computerized controller, and wherein thecomputerized controller stores instructions operable to cause thefinishing apparatus to perform the steps of positioning a machiningelement in contact with an exterior surface of a film cooled article,automatically moving the machining element along the exterior surfacewhile maintaining contact between the machining tool and the surface,identifying an actual position of at least one film opening based onsensory feedback from the machining element using a controller, andremoving material from the exterior surface at the film opening usingthe machining element, thereby creating a depression at the at least onefilm opening.

In a further embodiment of any of the foregoing embodiments, the atleast one of a touch sensor apparatus and a visual sensor apparatuscomprises both a touch sensor apparatus and a visual sensor apparatus.

In a further embodiment of any of the foregoing embodiments, thecomputerized controller further comprises a memory storing expected filmopening locations.

In a further embodiment of any of the foregoing embodiments, the atleast one film opening is at least one of a film hole and a film slot.

In a further embodiment of any of the foregoing embodiments, the touchsensor comprises at least one of a pressure based touch sensor,capacitive based touch sensor, and a resistive based touch sensor.

A film cooled article for a gas turbine according to an example of thepresent disclosure includes an article body having an internal coolingplenum operable to receive coolant and an exterior surface, at least onefilm opening connecting the internal plenum to the exterior surface andoperable to allow coolant from the internal plenum to be ejected fromthe film cooled article, and at least one depression aligned with the atleast one film opening, wherein the depression does not extend beyondthe film opening in at least one direction.

In a further embodiment of any of the foregoing embodiments, the atleast one film opening comprises a plurality of film holes, and whereinthe at least one depression comprises a plurality of depressions witheach depression corresponding to one of the film holes.

In a further embodiment of any of the foregoing embodiments, the atleast one depression includes a descending flank fore of the filmopening and an ascending flank at least partially aft of the filmopening, relative to an expected fluid flow direction.

In a further embodiment of any of the foregoing embodiments, the filmopening is at least partially positioned on the ascending flank.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a gas turbine engine.

FIG. 2A schematically illustrates a first film cooled blade.

FIG. 2B schematically illustrates a second film cooled blade.

FIG. 3 schematically illustrates a machining apparatus.

FIG. 4 illustrates a process for finishing a film cooled article.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct defined within a nacelle 15, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a first (or low) pressure compressor 44 and afirst (or low) pressure turbine 46. The inner shaft 40 is connected tothe fan 42 through a speed change mechanism, which in exemplary gasturbine engine 20 is illustrated as a geared architecture 48 to drivethe fan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a second (orhigh) pressure compressor 52 and a second (or high) pressure turbine 54.A combustor 56 is arranged in exemplary gas turbine 20 between the highpressure compressor 52 and the high pressure turbine 54. A mid-turbineframe 57 of the engine static structure 36 is arranged generally betweenthe high pressure turbine 54 and the low pressure turbine 46. Themid-turbine frame 57 further supports bearing systems 38 in the turbinesection 28. The inner shaft 40 and the outer shaft 50 are concentric androtate via bearing systems 38 about the engine central longitudinal axisA which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path C. The turbines 46, 54 rotationally drivethe respective low speed spool 30 and high speed spool 32 in response tothe expansion. It will be appreciated that each of the positions of thefan section 22, compressor section 24, combustor section 26, turbinesection 28, and fan drive gear system 48 may be varied. For example,gear system 48 may be located aft of combustor section 26 or even aft ofturbine section 28, and fan section 22 may be positioned forward or aftof the location of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five (5:1). Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tram° R)/(518.7°R)]̂0.5. The “Low corrected fan tip speed” as disclosed herein accordingto one non-limiting embodiment is less than about 1150 ft/second.

The turbine section 28 includes multiple stages, with each stage havingmultiple circumferentially spaced blades at a single axial position.Each of the blades is paired with a corresponding vane. In order toprevent overheating of the turbine blades, a film cooling system isimplemented within each turbine blade. Similar film cooling systems canbe implemented in the corresponding vane, or in other similarcomponents. Each film cooled component is referred to as a film cooledarticle.

In general, the airfoil of a film cooled blade or vane includes aninternal plenum and one or more rows of obliquely oriented, spanwiselydistributed coolant supply holes, referred to as film holes. Inalternate examples, the film holes can be replaced with slots. The filmholes penetrate the walls of an airfoil to establish fluid flowcommunication between the plenum and the flowpath. During engineoperation, the plenum receives coolant from the compressor anddistributes it to the film holes. The coolant issues from the holes as aseries of discrete jets. The oblique orientation of the film holescauses the coolant jets to enter the flowpath with a streamwisedirectional component, i.e. a component parallel to and in the samedirection as the dominant flow direction of the combustion gases.Ideally, the jets spread out laterally, i.e. spanwisely, to form alaterally continuous, flowing coolant film that hugs or adheres to theflowpath exposed surface of the airfoil. Multiple, rows of film holesare used in some examples, because the coolant film loses effectivenessas it flows along the airfoil surface.

The supply pressure of the coolant in the internal plenum exceeds thestatic pressure of the combustion gases flowing through the flowpath. Ifthe static pressure is not exceeded, the quantity of coolant flowingthrough the film holes is inadequate to satisfactorily film cool theairfoil surfaces. When the static pressure of the combustion gasesexceeds the coolant supply pressure, ingestion of harmful combustiongases into the plenum by way of the film holes can occur. This isreferred to as backflow. The intense heat of the ingested combustiongases can quickly and irreparably damage a blade or vane subjected tobackflow. However, the high coolant pressures required to guard againstinadequate coolant flow and backflow can cause the coolant jets topenetrate into the flowpath rather than adhere to the surface of theairfoil. As a result, a zone of the airfoil surface immediatelydownstream of each film hole becomes exposed to the combustion gases.

Each of the highly cohesive coolant jets that penetrate into theflowpath locally bifurcates the stream of combustion gases into a pairof minute, oppositely swirling vortices. The vertically flowingcombustion gases enter the exposed zone immediately downstream of thecoolant jets. Thus, the high pressure coolant jets not only leave partthe airfoil surface exposed, but actually entrain the hot, damaginggases into the exposed zone. In addition, the cohesiveness of the jetsimpedes their ability to spread out laterally (i.e. in the spanwisedirection) and coalesce into a spanwisely continuous film. As a result,strips of the airfoil surface spanwisely intermediate the film holesremain unprotected from the hot gases.

One way to encourage the coolant jets to adhere to the surface is toorient the film holes at a shallow angle relative to the surface. Withthe holes so oriented, the coolant jets will enter the flowpath in adirection more parallel than perpendicular to the surface.

FIGS. 2A and 2B illustrate detailed example turbine stage blades 100,including the film cooling system described generally above. Each of theblades 100 includes a root portion 110, a platform 112 and an airfoil114. The airfoil 114 includes a leading edge 116 and a trailing edge118. The airfoil 114 extends into the primary flowpath C, with theleading edge 116 upstream of the trailing edge 118. Each blade 100includes one or more internal plenums (not pictured) that receivescoolant from a coolant source such as a compressor bleed. In a fullyassembled turbine engine, such as the gas turbine engine 20, multiplecircumferentially distributed blades 100 radiate from a rotatable hub102, with each blade root portion 110 being captured in a correspondingslot in the hub 102.

During operation of the gas turbine engine 20, fluid in the primaryflowpath C is comprised of hot gaseous combustion products and flowsover the outer surfaces of the airfoil 114. The fluid flow over theairfoils 114 exert forces on the airfoil 114, thereby driving the hub102 to rotate.

The walls of the airfoil 114 each have a cold side with relatively coolinternal surfaces in contact with the coolant plenum. Each wall alsoincludes an external surface that is hot relative to the internalsurface. The external surfaces are the surfaces exposed to the fluidflowing through the primary flowpath C. The hot surface includes adepression 120 in the form of a trough. In alternate examples, thedepression 120 can be multiple individual dimples or multiple troughs.While illustrated herein as a trough extending substantially linearly inthe spanwise direction of the airfoil 114, other trough configurationscan be implemented including non-linear troughs. The depression 120includes a descending flank 122 fore of film holes 130 or slots 132 andan ascending flank 124 aft of the film holes 130 or slots 132. Therelative sizes of the depression 120, film holes 130, film slots 132,and the airfoil 114 are drawn for illustrative effect and are not drawnto scale.

A gently contoured ridge 126 may border the aft end of the depression120. The ridge 126 rises above, and then blends into a conventionalairfoil contour of the exterior surface of the airfoil 114. A floor 140,which is neither descending nor ascending, joins the flanks 122, 124. Inthe illustrated embodiment, the floor 140 is merely the juncture betweenthe descending and ascending flanks 122, 124, however the floor 140 mayhave a finite length.

Disposed within the depression 120 are multiple film holes 130 (FIG. 2A)or one or more film slots 132 (FIG. 2B) that provide a fluid pathwaybetween the interior plenums of the airfoil 114 and the flowpath C inwhich the airfoil 114 is disposed. The film holes 130 or slots 132penetrate the wall to convey coolant from the cold side to the hot side.Each film hole 130 or slot 132 has an intake opening on the internalsurface of the penetrated wall and a discharge opening in the form of anorifice on the external surface of the penetrated wall. Each dischargeopening is disposed on the ascending flank 124 of the depression 120.The film holes 130 or slots 132 are oriented so that coolant jetsdischarged from the film holes 130 or slots 132 enter the primaryflowpath C with a streamwise directional component, rather than with acounter-streamwise component. The streamwise directional component helpsensure that the coolant jets adhere to the hot surface rather thancollide and mix with the primary flowpath C.

In alternate examples using dimples in place of the illustrated trough,each dimple is placed over a single film hole 130 or slot 132, andprovides substantially the same features as the illustrated depression120.

In the examples illustrated in FIGS. 2A and 2B, the depression 120includes portions 127 that extend beyond the film holes 130 or slots132, and portions 128 between the film holes 130 or slots 132. In theportions 127, 128 of the depression 120 without a film hole 130 or slot132, fluid traveling through the primary flowpath C enters thedepression 120 via the descending flank 122, and then exits the troughvia the ascending flank 128. Due to the absence of a film hole 130 orslot 132, the fluid flowing through the depression 120 in these portions127, 128 is projected outward into the primary flowpatch C creating ahaystack effect. The haystack effect reduces the efficiency of the fluidflow through the primary flowpath and negatively impacts the coolingability of the blade 100.

While generally undesirable, the portions 127, 128 of the depression 120not aligned with a film hole 130 or slot 132 are unavoidable in previousmanufacturing techniques due to machining tolerances and requirements.In order to reduce or eliminate the negative impact, the automaticmachining technique disclosed herein, with regards to FIGS. 3 and 4, isutilized to create a depression 120 that is only aligned with the filmholes 130 or slots 132, and omit the portions 127, 128 of the depression120 that are not aligned with a film hole 130 or slot 132. That is tosay, in the finishing process, no material is removed from exteriorsurface of the airfoil other than material aligned with the film hole130 or the slot 132, thereby eliminating the extra portions 127, 128 ofthe depression 120. This reduces or eliminates the haystack effectdescribed above and improves the film cooling abilities of the filmcooled article.

With continued reference to FIG. 2, FIG. 3 schematically illustrates amachining apparatus 200 for machining the depression 120 into a castfilm cooled article, such as the film cooled blades 100 described above.The machining apparatus 200 includes a central control machine 210 withan articulating arm 220 extending therefrom. Attached to the end of thearticulating arm 220 is a machining tool 230. The machining tool 230includes a machining element 232 that capable of removing material fromthe cast film cooled article 250 according to any known material removaltechnique. The machining tool 230 further includes a touch sensor 236operable to detect when the machining tool 230 is in contact with thefilm cooled article 250, and a visual sensor 234 operable to provide avisual depiction of the film cooled article 250 being finished.

By way of example the touch sensor 236 can be pressure based, capacitivebased, resistive based, or any combination of the above sensingtechniques. Furthermore, any alternate touch sensing technique can beutilized instead of, or in conjunction with, the previously describedtouch sensing techniques and provide similar benefits. Similarly, thevisual sensor 234 can be any visual sensor capable of providing adetailed visual determination of the film cooled article 250 as thearticle is being finished.

Each of the sensors 234, 236 provide the sensed information to anelectronic controller 240 within the control machine 210. The electroniccontroller 240 uses a combination of the sensor information to ensurethat direct contact between the machining tool 230 and the film cooledarticle 250 being finished is maintained at all times in the finishingprocess. The visual sensor 234 and the touch sensor 236 are further usedby the electronic controller 240 to identify the actual position of thefilm holes 130 or slots 132 in real time, rather than relying onpre-programmed or expected positions that must account for castingtolerances. By maintaining contact with the article, repositioning ofthe machining tool 230 is minimized, and material can be removed at onlythe desired locations. This, in turn, reduces the tolerances on themachining process being utilized to create the depression 120 at thefilm holes 130 or slots 132.

While illustrated herein as a single control machine 210 utilizing asingle articulating arm 220, one of skill in the art having the benefitof this disclosure will appreciate that the control machine 210 canutilize any number of articulating device to precisely control theposition of the machining tool 230 based on the sensory inputs of thevisual sensor 234 and the touch sensor 236.

With continued reference to FIGS. 2 and 3, FIG. 4 illustrates a process300 for finishing a film cooled article, such as the turbine blades 100illustrated in FIG. 2A and 2B. Initially, a worker receives theunfinished film cooled article in a “receive a cast film cooled article”step 310. The cast film cooled article is cast with the interior plenumsand the film holes 130 or slots 132 connecting the interior coolingplenums to the exterior surface of the film cooled article. Due tonatural and unavoidable variances and tolerances in the casting process,the holes 130 or slots 132 will not be in the exact same location eachcast, even if an identical mold or casting technique is used. The workerthen mounts the film cooled article 250 to a machining apparatus, suchas the machining apparatus 200 illustrated in FIG. 3.

Once mounted, the machining tool 230 of the machining apparatus 200 isaligned with the cast film cooled article in an “align the cast filmcooled article with a machining tool” step 320. The alignment can bedone manually by the worker mounting the film cooled article 250, orautomatically by a controller 240 after the film cooled article has beenmounted. During the aligning, the machining tool 230 is brought near theunfinished film cooled article but not brought into contact with thefilm cooled article.

Once aligned, the controller 240 of the machining apparatus 200 takesover and places the machining element 232 in contact with the exteriorsurface of the cast film cooled article 250 in a “contact a surface ofthe film cooled article” 330. The machining apparatus 200 can detectwhen contact is made with the film cooled article 250 either using atouch sensor 236 to detect contact or a visual sensor 234 to detect adistance between the machining tool 230 and the cast film cooled article250. In alternate examples, this detection can be made using acombination of both sensor outputs. In either example, the contactdetermination is made in real time, as the machining tool 230 contactsthe cast film cooled article 250.

Once initial contact has been made between the machining tool 230 andthe cast film cooled article, the machining tool 230 is moved along thesurface of the cast film cooled article 250 to a film hole 130 or slot132 in a “move machining tool along the surface to a hole/slot” step340. During the movement, the controller 240 of the machining apparatus200 utilizes sensory feedback from at least one of the touch sensor 236and the visual sensor 234 to ensure that the machining tool 230 remainsin contact with the surface of the cast film cooled article.

The controller 240 also uses the sensory feedback to determine thepresence and exact location of a hole 130 or slot 132 at which adepression 120 needs to be machined out of the cast film cooled article.As with the contact sensing, the exact location of a hole 130 or slot132 can be determined based on the touch sensor 236 or the visual sensor234, thereby enabling precise positioning of the machining element 232,and allowing the depression 120 to be created only at the location ofthe film hole 130 or slot 132.

Once the precise location of the film hole 130 or slot 132 has beenidentified, the machining tool 230 removes material from the surface ofthe cast film cooled article at the film hole 130 or slot 132 in a“create depression at hole/slot” step 350. During the machining process,the touch sensor 236, the visual sensor 234, or a combination of thetwo, are used to ensure, in real time, that material is only removed atthe hole 130 or slot 132. The real time monitoring by the controller 240prevents creation of the excess portions 127, 128, described above withregards to the examples of FIGS. 2A and 2B.

Once the depression 120 has been created, the process 300 returns to themove machining tool along the surface to a hole/slot step 340 and themachining tool 230 is moved to the next film hole 130 or slot 132 in themanner described above.

In alternate examples, the controller 240 of the machining apparatus 200can be programmed to with expected approximate hole locations, anddetermine the exact locations in real time. In yet further alternateexample implementations, the controller 240 can be programmed to createdepressions of varying depths depending on the particular design of agiven film cooled article 250. In yet further alternate examples, thecontroller 240 can be programmed to skip certain film holes 130 or slots132 where no depression is desired.

While described above with general regards to film cooled blades andvanes for a turbine section of a gas turbine, one of skill in the arthaving the benefit of this disclosure will understand that themanufacturing process and end article described above can be any filmcooled article, and is not limited to a turbine stage blade or a turbinestage vane.

It is further understood that any of the above described concepts can beused alone or in combination with any or all of the other abovedescribed concepts. Although an embodiment of this invention has beendisclosed, a worker of ordinary skill in this art would recognize thatcertain modifications would come within the scope of this invention. Forthat reason, the following claims should be studied to determine thetrue scope and content of this invention.

1. A method for finishing a film cooled article comprising: providing afilm cooled article including at least one inner cooling plenum and atleast one opening connecting said inner cooling plenum to an exteriorsurface of the film cooled article; positioning a machining element incontact with said exterior surface of the film cooled article;automatically moving said machining element along said exterior surfacewhile maintaining contact between the machining tool and the surface;identifying an actual position of at least one film opening based onsensory feedback from the machining element using a controller; andremoving material from said exterior surface at said at least one filmopening using said machining element, thereby creating a depression atsaid at least one film opening.
 2. The method of claim 1, wherein thefilm cooled article is a cast film cooled article.
 3. The method ofclaim 1, wherein identifying the actual position of the at least onefilm opening based on sensory feedback from the machining elementcomprises interpreting sensor readings from at least one of a touchsensor apparatus and a visual sensor apparatus using the controller. 4.The method of claim 3, wherein identifying the actual position of the atleast one film opening based on sensory feedback from the machiningelement comprises the controller interpreting sensor readings from acombination of a touch sensor apparatus and a visual sensor apparatus.5. The method of claim 1, wherein identifying the actual position of theat least one film opening based on sensory feedback from the machiningelement, and removing material from said exterior surface at said filmopening using said machining element, thereby creating a depression atsaid film opening is repeated for each film opening of said film cooledarticle.
 6. The method of claim 1, wherein identifying the actualposition of the at least one film opening based on sensory feedback fromthe machining element, and removing material from said exterior surfaceat said film opening using said machining element, thereby creating adepression at said film opening is repeated for a subset of a pluralityfilm openings of said film cooled article.
 7. The method of claim 1,wherein removing material from said exterior surface at said filmopening using said machining element, thereby creating a depression atsaid film opening comprises removing material only at said filmopenings.
 8. The method of claim 1, wherein identifying an actualposition of at least one film opening based on sensory feedback from themachining element is performed by said controller in real time as saidmachining element is moved along the exterior surface.
 9. The method ofclaim 1, wherein automatically moving said machining element along saidexterior surface while maintaining contact between the machining tooland the surface comprises moving said machining element to an expectedposition of at least one film opening.
 10. The method of claim 9,wherein identifying an actual position of at least one film openingbased on sensory feedback from the machining element using a controllercomprises identifying the expected position and identifying the actualposition relative to the expected position.
 11. The method of claim 1,wherein removing material from said exterior surface at said filmopening using said machining element, thereby creating a depression atsaid film opening comprises creating a depression only at said filmopening.
 12. A finishing apparatus for a film cooled article comprising:a central control machine including a computerized controller; at leastone articulating device controlled by said central control machine; amachining tool mounted to said articulating device, such that saidarticulating device is operable to move said machining tool; at leastone of a touch sensor apparatus and a visual sensor apparatus mounted tosaid machining tool and communicatively coupled to the computerizedcontroller; and wherein said computerized controller stores instructionsoperable to cause said finishing apparatus to perform the steps of:positioning a machining element in contact with an exterior surface of afilm cooled article; automatically moving said machining element alongsaid exterior surface while maintaining contact between the machiningtool and the surface; identifying an actual position of at least onefilm opening based on sensory feedback from the machining element usinga controller; and removing material from said exterior surface at saidfilm opening using said machining element, thereby creating a depressionat said at least one film opening.
 13. The finishing apparatus of claim12, wherein the at least one of a touch sensor apparatus and a visualsensor apparatus comprises both a touch sensor apparatus and a visualsensor apparatus.
 14. The finishing apparatus of claim 12, wherein thecomputerized controller further comprises a memory storing expected filmopening locations.
 15. The finishing apparatus of claim 12, wherein theat least one film opening is at least one of a film hole and a filmslot.
 16. The finishing apparatus of claim 12, wherein the touch sensorcomprises at least one of a pressure based touch sensor, capacitivebased touch sensor, and a resistive based touch sensor.
 17. A filmcooled article for a gas turbine comprising: an article body having aninternal cooling plenum operable to receive coolant and an exteriorsurface; at least one film opening connecting said internal plenum tosaid exterior surface and operable to allow coolant from said internalplenum to be ejected from said film cooled article; at least onedepression aligned with said at least one film opening, wherein saiddepression does not extend beyond said film opening in at least onedirection.
 18. The film cooled article of claim 17, wherein the at leastone film opening comprises a plurality of film holes, and wherein the atleast one depression comprises a plurality of depressions with eachdepression corresponding to one of said film holes.
 19. The film cooledarticle of claim 17, wherein the at least one depression includes adescending flank fore of the film opening and an ascending flank atleast partially aft of the film opening, relative to an expected fluidflow direction.
 20. The film cooled article of claim 19, wherein saidfilm opening is at least partially positioned on said ascending flank.